HP 3000 Manuals

Installing and Configuring HP X.400 Administrator's Guide

X.400 Protocols 

As an OSI standard, X.400 uses the services provided by the layers 1-5 of
the OSI reference model.  This is either X.25 or IEEE 802.3 at the lower
three layers, with Transport Class0, 1, 2, or 4 at layer 4 and the Basic
Activity Subsetof Session at layer 5.  The X.400 standard cover the
Presentation and Application layers of the OSI model, layers 6 and 7.
The protocols used in X.400 are P1, P2, and RTS (Reliable Transfer
Service).


          Figure 2-7.  X.400 OSI Protocols 

The RTS protocol transfers the higher layer units of information between
two MTAs.  It is essentially a file transfer mechanism between two MTAs.
The files themselves contain encoded information for the MTA and UA. The
protocol involved in the MTS is known as P1.  This protocol allows a
message to be delivered to the MTA with which the destination UA is
associated and specifies other interactions necessary to provide X.400
services.  Between UAs the protocol is known as P2.  This protocol
specifies the format for the heading, multipart body types, and general
content protocol to support the IPM services.

MPE/iX 5.0 Documentation